Procedure for measuring a measured variable in a process step of a manufacturing process and measurement chain for carrying out said procedure

Abstract

A procedure for measuring a measured variable in a process step of a manufacturing process uses a measurement chain with an evaluation unit and a plurality of measurement units having a sensor, a converter unit and a secondary antenna. The evaluation unit has a primary antenna. A measurement unit is positioned for measuring the measured variable and automatically coupled to the evaluation unit by establishing a transmission connection between the secondary antenna and the primary antenna. The sensor automatically generates measurement signals indicative of the measured variable. The converter unit automatically converts the measurement signals into measurement data, which the secondary antenna automatically transmits to the primary antenna.

What is claimed is: 
     
         1 . A method for using a measurement chain, which includes an evaluation unit and a plurality of measurement units, for measuring a measured variable occurring in a process step of a manufacturing process and resulting from an interaction of a machine tool and a workpiece during the manufacturing process, wherein the evaluation unit includes a primary antenna, wherein each of the respective measurement units includes a respective sensor, a respective converter unit and a respective secondary antenna, the method comprising the following steps:
 disposing the workpiece and a tool of the machine tool relative to each other so that a measurement unit is positioned in a measuring position for measuring the measured variable;   establishing a transmission connection between the respective secondary antenna of the respective measurement unit and the primary antenna so as to automatically couple the respective positioned measurement unit with the evaluation unit;   using a respective sensor of the respective positioned measurement unit to automatically generate measurement signals representing the measured variable;   using a respective converter unit of the respective positioned measurement unit to automatically convert the measurement signals into measurement data; and   automatically transmitting the measurement data by the respective secondary antenna of the respective positioned measurement unit to the primary antenna.   
     
     
         2 . A machine tool comprising:
 a measurement chain which includes an evaluation unit and a plurality of measurement units for measuring a measured variable occurring in a process step of a manufacturing process and resulting from an interaction of the machine tool and a workpiece during the manufacturing process, wherein the evaluation unit includes a primary antenna;   wherein each of the respective measurement units includes a respective sensor, a respective converter unit and a respective secondary antenna;   wherein each of the respective measurement units is configured to be positioned in a measuring position where the respective measurement unit can be coupled to the evaluation unit for establishing a transmission connection between the respective secondary antenna and the primary antenna.   
     
     
         3 . The machine tool according to  claim 2 , wherein the primary antenna generates an electromagnetic alternating field and transmits the electromagnetic alternating field; wherein a range of the electromagnetic alternating field is limited in such a way that only those respective measurement units that are completely positioned in the measuring position are able to receive the electromagnetic alternating field. 
     
     
         4 . The machine tool according to  claim 3 , wherein as soon as and as long as the respective secondary antenna receives the electromagnetic alternating field, the respective measurement unit is supplied with electrical energy; and wherein the respective measurement unit is configured to be supplied with sufficient electrical energy to operate the respective measurement unit within a ready for operation time of 100 ms, preferably within a ready for operation time of 20 ms. 
     
     
         5 . The machine tool according to  claim 4 , wherein the secondary antenna is configured to establish the transmission connection to the primary antenna when the respective measurement unit is ready for operation, wherein the respective secondary antenna is configured to transmit an identification number unambiguously identifying the measurement unit to the primary antenna; wherein the primary antenna is configured to receive an identification number and forward the identification number to the evaluation unit; and wherein the evaluation unit is configured to identify the respective measurement unit on the basis of the received and transmitted identification number. 
     
     
         6 . The machine tool according to  claim 2 , wherein the machine tool includes a plurality of tool holders; wherein each respective tool holder is configured to accommodate a tool; wherein each measurement unit is associated with each respective tool holder; wherein a respective sensor of the respective measurement unit associated with the respective tool holder is arranged at each respective tool holder; wherein for a respective measurement unit positioned in the measuring position, the respective sensor of the respective measurement unit positioned in the measuring position is configured to measure the measured variable that acts onto the tool during a process step; and wherein the respective converter unit and the respective secondary antenna of the respective measurement unit are arranged at a spatial distance from the respective sensor. 
     
     
         7 . The machine tool according to  claim 6 , further comprising a turret that is configured to be rotatable about a longitudinal axis; wherein the respective tool holders are arranged on the turret and configured to be rotated with the turret about the longitudinal axis of rotation; and wherein the turret is configured so that rotating the turret about the axis of rotation facilitates sequential positioning of the tools on the workpiece one after the other in time. 
     
     
         8 . The machine tool according to  claim 2 , further comprising a plurality of respective clamping units; wherein each respective clamping unit is configured to accommodate a respective workpiece; a respective measurement unit is disposed in association with each respective clamping unit; wherein a respective sensor of the respective measurement unit is associated with the respective clamping unit and is disposed at each respective clamping unit; wherein for a measurement unit positioned in the measuring position, the respective sensor of the respective measurement unit positioned in the measuring position is configured to measure the measured variable that acts onto the respective workpiece during a process step; and wherein the respective converter unit and the respective secondary antenna of the respective measurement unit are arranged at a spatial distance from the respective sensor. 
     
     
         9 . The machine tool according to  claim 8 , further comprising a carrier unit; and wherein each of the plurality of clamping units is configured to be changeably attached to the carrier unit. 
     
     
         10 . The machine tool according to  claim 2 , further comprising a plurality of changeable heads; wherein each respective one of the plurality of changeable heads is configured to accommodate a respective tool of a plurality of tools; wherein a measurement unit is associated with each respective changeable head; wherein a sensor of the measurement unit associated with the changeable head is arranged at each changeable head; wherein for a measurement unit positioned in the measuring position, the sensor of the measurement unit positioned in the measuring position is configured to measure the measured variable that acts onto the tool during a process step; and wherein the converter unit and the secondary antenna of the measurement unit are arranged at a spatial distance from the sensor. 
     
     
         11 . The machine tool according to  claim 10 , wherein the machine tool is an industrial robot that includes a manipulator; and wherein each of the plurality of changeable heads is configured to be changeably attached at the manipulator. 
     
     
         12 . The machine tool according to  claim 6 , further comprising a primary housing and a secondary housing, wherein the converter unit and the secondary antenna are arranged in the secondary housing; wherein the primary antenna is arranged in the primary housing; and wherein the secondary housing and the primary housing are configured to be movable relative to each other. 
     
     
         13 . The machine tool according to  claim 12 , for a measurement unit positioned in the measuring position, the secondary housing of the measurement unit positioned in the measuring position is positioned at a transmission distance from the primary housing, which transmission distance is configured to be conducive to transmission of signals between the primary antenna and each of the secondary antennas. 
     
     
         14 . The machine tool according to  claim 13 , wherein the primary antenna is configured to generate an electromagnetic alternating field; and wherein the transmission distance between the secondary housing of the measurement unit positioned in the measuring position and the primary housing is disposed within the range of a detectable magnitude of the electromagnetic alternating field. 
     
     
         15 . The machine tool according to  claim 6 , wherein each sensor is a piezoelectric sensor that includes piezoelectric material; wherein when the measured variable acts onto the piezoelectric material in the form of tensile and/or compressive loads and under the action of the measured variable then the piezoelectric material is configured to generate measurement signals in the form of electrical charge; wherein the converter unit includes a charge amplifier that is configured to amplify the electrical charge of the piezoelectric sensor to become an amplified charge; wherein the charge amplifier is configured to convert the amplified charge into an electrical voltage; wherein the converter unit is configured to digitize the electrical voltage into measurement data; wherein the piezoelectric sensor is configured to measure the measured variable with a high dynamic measurement resolution of up to 35 kHz; and wherein the secondary antenna is configured to transmit the measurement data to the primary antenna at a transmission rate of up to 424 kBit/s. 
     
     
         16 . The machine tool according to  claim 6 , wherein the sensor is a piezoelectric sensor that includes piezoelectric material; wherein when the measured variable acts onto the piezoelectric material in the form of tensile and/or compressive loads and under the action of the measured variable then the piezoelectric material is configured to generate measurement signals in the form of electrical charge; wherein the converter unit includes a charge amplifier that is configured to amplify the electrical charge of the piezoelectric sensor to become an amplified charge; wherein the charge amplifier is configured to converts the amplified charge into an electrical voltage; wherein the converter unit is configured to digitize the electrical voltage into measurement data; wherein the converter unit is configured to generate unit data that indicates the unit of the measured variable for which the converter unit has converted and digitized measurement signals into measurement data; wherein the measurement unit includes a data memory unit that stores serial number data of the converter unit; wherein the converter unit is configured to read out calibration data of the sensor from the data memory unit of the measurement unit; wherein that the converter unit reads out serial number data of the converter unit from the data memory unit; and wherein the secondary antenna is configured to transmit the unit data, the calibration data and the serial number data together with the measurement data to the primary antenna. 
     
     
         17 . The method according to  claim 1 , wherein the machine tool is a lathe that is adapted to machine a workpiece by a plurality of tools in a plurality of process steps in a chronological sequence, and further comprising the step of positioning a tool on the workpiece in each process step, wherein a measurement unit is associated with each tool. 
     
     
         18 . The method according to  claim 1 , wherein the machine tool is a clamping system that includes a carrier unit and a plurality of clamping units, wherein each one of the plurality of clamping units is changeably mounted on the carrier unit. 
     
     
         19 . The method according to  claim 1 , wherein the machine tool is an industrial robot that includes a manipulator and a plurality of changeable heads, wherein each of the plurality of changeable heads is configured to be changeably mounted on the manipulator by a coupling means that is configured to be changed on the manipulator within a setup time of 500 ms.